A system to reconstruct images from projection data is proposed. The key feature of this system is its speed of operation. The goal of the system is image reconstruction in a video frame time (1/30 sec). The system could be coupled to x-ray computed tomography (CT) systems or Nuclear Magnetic Resonance (NMR) imaging equipment to provide essentially instantaneous viewing of the images after collection of the projection data. The recent emergence of very fast x-ray CT scanners for cardiac imaging would couple nicely to the proposed reconstruction system and would create a system capable of CT flouroscopy. Dynamic studies and real-time interaction with the patient would be possible. The proposed reconstruction system is basically an electro-optic system that implements the filtered back-projection algorithm. The final reconstructed image is a video signal and can be viewed, manipulated, and recorded in the same manner as present image data. Preliminary studies and analysis indicate that the spatial and contrast resolution of the images produced by the proposed system should be comparable to those produced by conventional digital methods.